The present invention relates to a structure of an output shaft through which driving force outputted from a vehicular automatic transmission is transmitted to driving wheels.
Generally, a conventional output shaft of an automatic transmission is configured as shown on page I-7 in a publication xe2x80x9cMaintenance Manual of Nissan Full-Range Electronic Control Automatic Transmissionsxe2x80x9d published on March 1987. FIG. 13 shows a schematic structure of this conventional automatic transmission including a conventional output shaft 108. The automatic transmission comprises a converter case 101, a transmission case 102 and a rear extension 103. An input shaft 107 transmits a driving force of an engine from a torque converter 104 in the converter case 101 to a gear train 105 in the transmission case 102. The driving force is varied in rotation speed by the gear train 105 and is transmitted to driving wheels through the output shaft 108 and a flange companion. The output shaft 108 has oil passages for lubricating sliding portions of the automatic transmission. A parking gear 109 for fixing driving wheels during a parking condition is fixedly connected to the output shaft 108 in the rear extension 103.
However, since this conventional output shaft 108 has been configured to one piece structure extending from the gear train 105 to the flange companion 110, it is necessary to change the output shaft 108 when an axial dimension of an automatic transmission is changed according to the change of vehicle variety. Further, when this output shaft structure is employed to an automatic transmission for four wheel drive (4WD) vehicle, it is necessary to install a 4WD unit at a part corresponding to the rear extension 103. However, this 4WD arrangement requires to completely replace the output shaft 108 with a different output shaft for 4WD. Furthermore, this conventional one-piece structure of the output shaft 108 increases difficulties in machining oil passages according to the elongation of the axial dimension of the output shaft 108. Additionally, since the output shaft 108 is directly connected to the flange companion 110, there is a tendency that the gear train 105 receives the load input including bending force and thrust force from driving wheels.
It is therefore an object of the present invention to provide an improved output shaft structure which solves the above-mentioned problems.
An output shaft of an automatic transmission according to the present invention comprises a first output shaft which outputs a driving force from a gear train of an automatic transmission and a second output shaft which is connected to the first output shaft so as to be movable in an axial direction and to be fixed in a rotational direction with respect to the first output shaft. The second output shaft is integral with a parking gear which fixes the second output shaft in rotation when the automatic transmission is set at a parking position.